1. Field of the Invention
The present invention relates to a substrate processing apparatus, and more particularly, to a substrate processing apparatus for etching a surface of a substrate such as a silicon wafer by utilizing plasma, and for forming a thin film on the surface of the substrate by utilizing plasma.
2. Description of the Related Art
As a substrate processing apparatus for processing a silicon wafer utilizing plasma, there is an apparatus as shown in FIGS. 1 and 2. FIG. 1 is a schematic explanatory transverse sectional view of a vertical type substrate processing furnace of a conventional substrate processing apparatus. FIG. 2 is a schematic vertical sectional view taken along the line A-A in FIG. 1.
A thin and long buffer chamber 237 is provided in a vertical direction near an inner wall surface of a reaction tube 203. In the buffer chamber 237, two rod-like discharge electrodes 269 covered with electrode protection tubes 275 made of dielectric, and a gas nozzle 233 for obtaining a uniform gas flow in the buffer chamber 237 are disposed.
High frequency electric power generated by an oscillator of a high frequency power supply 273 is applied to ends 301 of the discharge electrodes 269 to generate plasma 224 between the discharge electrodes 269 in the buffer chamber 237, and thereby to excite reaction gas supplied from a gas nozzle 233 with plasma, and the plasma-excited reaction gas is supplied to wafers 200 which are substrates to be processed in the reaction tube 203 from a gas supply hole 248a formed in a sidewall of the buffer chamber 237.
While the wafers 200 are processed, gas in the electrode protection tubes 275 is continuously replaced by inert gas to prevent the discharge electrode from being oxidized.
However, the inside of the reaction tube 203 is heated to about 600 to 900° C. to process the wafers 200, and as a result, the discharge electrodes 269 are discolored or deteriorated due to slight residual oxygen in the inert gas in the electrode protection tubes 275 or a sealing failure at a portion from which the discharge electrode 269 is pulled outside, and the performance of the electrodes can not be maintained.
As conventional techniques, other than the above-described technique, there are one in which a flexible electrode (weaved electrode) is used (Japanese Patent Application No. 2004-055446 (International Application No. PCT/JP 2005/002306)), and one in which high frequency electric power is supplied through a power transformer (Japanese Patent Application No. 2003-056772 (International Application No. PCT/JP 2004/002735, International Laid-open No. WO2004/079813)).    [Patent document 1] Japanese Patent Application No. 2004-055446 (International Application No. PCT/JP 2005/002306)    [Patent document 2] Japanese Patent Application No. 2003-056772 (International Application No. PCT/JP 2004/002735, International Laid-open No. WO2004/079813)